US4287811A - Brake booster - Google Patents

Brake booster Download PDF

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Publication number
US4287811A
US4287811A US06/071,489 US7148979A US4287811A US 4287811 A US4287811 A US 4287811A US 7148979 A US7148979 A US 7148979A US 4287811 A US4287811 A US 4287811A
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US
United States
Prior art keywords
piston
power piston
control
locking member
power
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US06/071,489
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English (en)
Inventor
Masayoshi Katagiri
Osamu Ogura
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Toyota Motor Corp
Aisin Corp
Original Assignee
Aisin Seiki Co Ltd
Toyota Jidosha Kogyo KK
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Aisin Seiki Co Ltd, Toyota Jidosha Kogyo KK filed Critical Aisin Seiki Co Ltd
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Publication of US4287811A publication Critical patent/US4287811A/en
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Expired - Lifetime legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T13/00—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems
    • B60T13/10—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with fluid assistance, drive, or release
    • B60T13/24—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with fluid assistance, drive, or release the fluid being gaseous
    • B60T13/46—Vacuum systems
    • B60T13/52—Vacuum systems indirect, i.e. vacuum booster units
    • B60T13/569—Vacuum systems indirect, i.e. vacuum booster units characterised by piston details, e.g. construction, mounting of diaphragm

Definitions

  • This invention relates to a brake booster for boosting a brake operational force by means of utilizing gas pressure, more particularly, to an improvement in a stroke enlarging type booster.
  • a stroke enlarging type booster herein referred to is a brake booster wherein a power piston is disposed in a manner of bisecting a booster casing so as to be operated by a pressure difference between the pair of divided chambers.
  • the power piston is separated from a controlling mechanism which controls the pressure difference due to an operation of an input member, so as to be shiftable in relation to the controlling mechanism.
  • This stroke enlarging type brake booster is capable of obtaining a larger output stroke than the stroke input, unlike ordinary brake boosters wherein the output stroke is always the same as or smaller than the input stroke.
  • This type of stroke enlarging brake booster is described in pending U.S. patent application Nos. 919,071, now U.S. Pat. No. 4,242,943, and 46,046. In the former a spring means for transmitting a part of operational force of the power piston to the controlling mechanism is used, while in the latter it is not. Both boosters are almost identical otherwise.
  • a primary object of this invention to provide a stroke enlarging type brake booster wherein an output force larger than the output force at the critical point can be obtained without inviting an unnatural increasing of the pedal stroke and also no disadvantage arises even in the operation thereof in the range beyond the critical point.
  • the brake booster in accordance with this invention is constructed with a control piston, as a main body of the controlling mechanism, a power piston disposed relatively movably thereto, a locking member retained by either of the control piston or the power piston and operated between a first position and the second position due to the pressure difference in the chambers on opposite sides of the power piston, and blocking at its first position the relative movement of the two pistons by being engaged with an engaging portion disposed on the opposite one of the two pistons from that on which it is retained, and resilient means, which normally retains the locking member at its second position and allows the locking member, when the pressure difference in the chambers on opposite sides of the power piston has exceeded the predetermined value, to move to its first position for engaging with the engaging portion.
  • the brake booster of this invention can also be constructed from the following components:
  • a power piston disposed in a manner of dividing the inside room of a casing into two, a constant pressure chamber and a variable pressure chamber, normally urged by resilient means toward the retracted position, and advanced in the axial direction, resisting the action of the resilient means, in accordance with the pressure difference in the two chambers;
  • control piston disposed relatively movably in the axial direction to the power piston within a pre-limited distance, normally retained at the retracted position by resilient means, and forwardly movable together with the power piston when the pre-limited distance relatively movable thereto has been reduced to zero;
  • a control valve operable in response to relative movement between the control piston and the input member to control the pressure difference in the two chambers on opposite sides of the power piston;
  • a transmitting mechanism for transmitting forces applied by the control piston and the input member, while allowing relative movement within the limited distance between the control piston and the input member;
  • a reaction lever abutting at one end thereof to the output portion of the transmitting mechanism, abutting at the other end thereof to the output portion of the power piston, and abutting at the middle portion thereof to the input portion of the output member, for transmitting the output force from the transmitting mechanism and the power piston to the output member, while allowing relative movement between the transmitting mechanism and the power piston;
  • a locking member retained by the control piston movably in a radial direction thereof, for blocking relative movement between both pistons, when being in the advanced position, by engagement with the engaging portion formed on the power piston;
  • operating force imparting means for imparting an operating force to the locking member for advancing it to an advanced position, owing to the difference of pressure in the two chambers on opposite sides of the power piston;
  • (10) resilient means normally holding the locking member at the retracted position, and allowing the locking member to advance to the forward position when the operational force toward the advanced position by the operating force imparting means has exceeded a pre-limited value.
  • This invention succeeds in eliminating the disadvantage in the previously invented stroke enlarging type brake booster of a temporary rapid increasing of the pedal stroke in the range beyond the limit of the boosting force. It has largely enhanced the practicability of the brake booster of the stroke enlarging type, having made possible the manufacturing of an ideal brake mechanism which is operated by a fairly small stroke for producing a large braking effect.
  • FIG. 1 is an axial sectional view of an embodiment of a booster in accordance with this invention
  • FIG. 2 is a cross section of FIG. 1 taken along the section line II--II;
  • FIG. 3 is an axial sectional view of the booster in FIG. 1 in a different operational condition
  • FIG. 4 is a graph for illustrating the relation between the input stroke and the output stroke of the booster shown in FIG. 1;
  • FIG. 5 is an enlarged axial sectional view of an essential part of another embodiment of a brake booster.
  • FIG. 6 (i), (ii), and (iii) are graphs for explaining the operation of the brake booster of FIG. 5.
  • the booster 100 is provided with a gas-tight casing 3, the inner chamber of which is divided into two parts by a diaphragm type power piston 4.
  • One of the chambers is made into a constant pressure chamber 6 by being connected to a vacuum source or a negative pressure source such as an intake manifold of the engine, a vacuum pump, etc., via a pipe joint 5.
  • the other chamber is made into a variable pressure chamber 7, by means of being communicated selectively to the constant pressure chamber 6 or to the ambient atmosphere, by a later described control valve.
  • a control piston 9 which is a main body of the controlling mechanism.
  • the control piston 9 has its backward movement limit position (retracted position) fixed by its abutting a stopper plate 12 on the inner surface of the casing 3, which is fixed with an E-shape ring 11 on the outer periphery of the control piston.
  • the power piston 4 also has its backward movement limit position fixed by it abutting, via the stopper plate 12, on the inner surface of the casing 3, and normally is retained at the backward movement limit position (retracted position) by the action of return spring 8, via a spring holder 13 which spans both pistons 4, 9.
  • the power piston 4 is allowed to advance in relation to the control piston 9, the advance amount being regulated by the abutment of the power piston 4 on a cushion ring 14 fitted on the control piston 9.
  • the controlling mechanism is composed of a control valve 20 and a transmitting mechanism 30.
  • the control valve 20 is made up of a first valve seat 21 formed on the control piston 9, a second valve seat 23 formed on a valve plunger 22 which is slidably fitted in the control piston 9, and a valve element 24 of resilient material commonly disposed to the valve seats 21, 23.
  • the valve element 24 is urged toward the valve seats 21, 23 by a compression spring 29, being normally abutted on the second valve seat 23 and separated from the first valve seat 21, while the brake operational force is not applied to the operating rod 1 which is fixed to the valve plunger 22 at the tip thereof.
  • the variable pressure chamber 7 is isolated from the ambient atmosphere and is communicated, via passageways 25, 26, with the constant pressure chamber 6, being at the same negative pressure as the constant pressure chamber 6.
  • variable pressure chamber 7 When the operating rod 1 is advanced forward the first valve seat 21 abuts on the valve element 24 and the second valve seat 23 is separated from the valve element 24, separating the variable pressure chamber 7 from the constant pressure chamber 6 and communicating it with the ambient atmosphere.
  • the pressure of the variable pressure chamber 7 will be raised because of the in flow of air sucked from an air sucking opening 16 in a boot 15 into the variable pressure chamber 7.
  • the forward movement limit of the valve plunger 22 is regulated by a stopper 27 secured on the control piston 9.
  • the transmitting mechanism 30 is composed of a small plunger 31, a part of the valve plunger 22, slidably fitted in a small diametered bore portion of the control piston 9, a large plunger 32, slidably fitted in a large diametered bore portion of the control piston 9, and a reaction disc 33 sandwiched between the both plungers 31, 32.
  • the small plunger 31 of the valve plunger 22 transmits a brake operational force from the operating rod 1 to the reaction disc 33, the latter working similarly as a fluid filled in a space encompassed by the both plungers 31, 32 and the control piston 9.
  • the reaction disc 33 transmits a resultant force from the operating rod 1 and the control piston 9 to the large plunger 32, while allowing a minute relative movement between the small plunger 31 and the control piston 9, in other words, the relative movement between the operating rod 1 and the control piston 9.
  • the large plunger 32 is provided with a rod portion 34 forwardly protruding in the central portion thereof, which rod portion 34 slidably retains the rear end of the push rod 2.
  • the output force from the large plunger 32 and the power piston 4 is transmitted by a reaction lever 41 to the push rod 2.
  • the reaction lever 41 abuts, at one end thereof, on an output portion 42 of the power piston 4, at the other end thereof, on an output portion 43 of the large plunger 32, and, at the middle portion thereof, on a plate 44, which is an input portion of the push rod 2.
  • the reaction lever 41 thus transmits a resultant force from the power piston 4 and the large plunger 32, while allowing relative movement between both, to the push rod 2.
  • Numeral 45 designates a retainer plate, secured to the power piston 4 with a screw 46, for retaining the spring holder 13 at a predetermined position, and for preventing the plate 44, an input portion of the push rod 2, from separating away from the power piston 4 beyond a predetermined limit.
  • cylinder portions 51 are, as shown in FIG. 2, radially disposed as a protrusion with an equal angular distance of 120°.
  • a cylinder bore which is communicated with the variable pressure chamber 7 via a passageway 52 as shown in FIG. 1 is formed in each cylinder portion 51.
  • a lock piston 53 is respectively fitted in the cylinder bore, in a movable manner in the perpendicular direction to the movement direction of control piston 9, that is in the radial direction of the control piston 9.
  • the lock piston 53 is provided, in the central portion thereof, with an engaging projection 54, which projects through the central part of a spring retainer 56 secured to the cylinder portion 51 via an E-shape ring 55'.
  • a compression spring 57 is mounted between the spring retainer 56 and the lock piston 53 for normally biasing the latter toward the retracted position.
  • a rib 58 of the power piston 4 is, formed an engaging hole 59 at a position where it confronts the engaging projection 54 of the lock piston 53 when the power piston 4 is advanced forwardly in relation to the control piston 9 to the point where it abuts on the cushion ring 14 fitted on the control piston 9.
  • variable pressure chamber 7 is therefore in communication with the constant pressure chamber 6 and contains a negative pressure, producing no pressure difference on opposite sides of the power piston 4.
  • the power piston 4 and the control piston 9 are both retained at the retracted position respectively due to the action of the return spring 8.
  • the braking fluid in the master cylinder 102 is supplied to a not-illustrated hydraulic system for nullifying the brake clearance and filling up the necessary amount of consumption fluid caused by the initial stage deformation of the piston cup, etc.
  • this piston stroke of the master cylinder 102 in this process is called an initial stroke
  • one of the main features of the booster 100 of this invention lies in that the initial stroke in question can be obtained by a small amount of input stroke (stroke of the operating rod 1).
  • the power piston 4 comes to an abutment on the cushion ring 14 fitted on the control piston 9, and it will, once abutted thereon, begin to move together with the control piston 9.
  • the operating mode of the booster 100 is entirely identical to that of ordinary boosters.
  • the operating rod 1 and the power piston 4 push forward the push rod 2, while sharing the force at a ratio determined by the reaction lever 41 and the reaction disc 33.
  • the output stroke increases at the same rate as the input stroke as shown in FIG. 4.
  • the lock piston 53 advances, resisting the biasing force of the compression spring 57, and its engaging projection 54 fits into the engaging hole 59 in the power piston 4.
  • the lock piston 53 which is affected at the front side thereof by the pressure in the constant pressure chamber 6 and at the rear side by the pressure in the vicinity of the valve plunger of the variable pressure chamber 7, will be moved to the advanced position, owing to a domination of the lock-piston-actuating force over the biasing force of the compression spring 57, when the pressure in the passage 52 and in the variable pressure chamber 7 is raised in response to the progressive operation of the operating rod 1 and the difference between that pressure and the pressure in the constant pressure chamber 6 has reached a predetermined value.
  • This makes possible the fitting of the engaging projection 54 of the lock piston 53 into the engaging hole 59 of the power piston 4.
  • the power piston 4 begins to move back (retract) actually, resulting in a stoppage of the plate 44 and the push rod 2 regardless of the forward movement of the large plunger 32. It means an absorption of the movement of the large plunger 32 by the retraction of the power piston 4, which will be continued until the output portion 43 abuts on the plate 44 having the reaction lever 41 sandwiched therebetween. It results in an appearance of an idle stroke wherein no increase of stroke is seen in the push rod 2 irrespective of stroke increase in the operating rod 1, as shown in FIG. 4 with a two-dot-chain line, so that the braking hydraulic pressure in the master cylinder 102 does not rise.
  • the push rod 2 is thus pushed forward, via the plate 44, by this consolidated one body, so the output stroke is increased even at this stage at the same rate as the input stroke increases.
  • the output force of the booster 100 increases by the same amount as the increase of the brake operating force.
  • the lock piston 53 is utilized as a locking member, and the passage 52 disposed at the back side of the lock piston 53 for leading the pressure in the variable pressure chamber 7 is utilized as a means for operating the locking member.
  • the locking member is not necessarily limited to a form of piston which is directly operated by the pressure difference between the constant pressure chamber and the variable pressure chamber, but may be a member indirectly actuated by a piston, etc., which is operated by the pressure difference between the two chambers.
  • the engaging portion for engaging with the locking member is not limited to the engaging hole as in the aforementioned embodiment, a mere rib formed on the power piston or the control piston or a C-shape ring fitted in an annular groove of those pistons can also be used.

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  • Engineering & Computer Science (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Braking Systems And Boosters (AREA)
US06/071,489 1979-02-28 1979-08-31 Brake booster Expired - Lifetime US4287811A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP54-22633 1979-02-28
JP2263379A JPS55114653A (en) 1979-02-28 1979-02-28 Brake booster

Publications (1)

Publication Number Publication Date
US4287811A true US4287811A (en) 1981-09-08

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Application Number Title Priority Date Filing Date
US06/071,489 Expired - Lifetime US4287811A (en) 1979-02-28 1979-08-31 Brake booster

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US (1) US4287811A (enrdf_load_stackoverflow)
JP (1) JPS55114653A (enrdf_load_stackoverflow)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4387625A (en) * 1980-02-09 1983-06-14 Toyota Jidosha Kogyo Kabushiki Kaisha Brake booster
US4398449A (en) * 1980-01-21 1983-08-16 Tokico Ltd. Pneumatic servo booster
US4416188A (en) * 1980-05-26 1983-11-22 Toyota Jidosha Kogyo Kabushiki Kaisha Brake booster
EP0140187A1 (en) * 1983-10-05 1985-05-08 Nissan Motor Co., Ltd. Brake booster
US4590845A (en) * 1979-12-14 1986-05-27 Tokico Ltd. Pneumatic servo booster
US4643076A (en) * 1980-04-21 1987-02-17 Jidosha Kiki Co., Ltd. Controller for valve mechanism of brake booster
US4756231A (en) * 1985-08-13 1988-07-12 Nissan Motor Co., Ltd. Pneumatic brake booster
EP0368679A3 (en) * 1988-11-11 1991-06-26 Tokico Ltd. Tandem type brake booster
US5226291A (en) * 1991-12-17 1993-07-13 General Motors Corporation Vacuum booster diaphragm/support plate retention method
US20140062176A1 (en) * 2012-08-28 2014-03-06 Hitachi Automotive Systems, Ltd. Brake Control Apparatus
US20190031168A1 (en) * 2016-01-25 2019-01-31 Advics Co., Ltd. Negative-pressure type booster device

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3143930A (en) * 1962-03-21 1964-08-11 Kelsey Hayes Co Fluid pressure motor mechanism
US3183789A (en) * 1963-05-14 1965-05-18 Kelsey Hayes Co Fluid pressure motor mechanism
US3452646A (en) * 1966-12-29 1969-07-01 Bendix Corp Valve and spring retainer
US3845692A (en) * 1972-04-07 1974-11-05 Nisshin Kogyo Kk Vacuum suspended type servo-motor

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3143930A (en) * 1962-03-21 1964-08-11 Kelsey Hayes Co Fluid pressure motor mechanism
US3183789A (en) * 1963-05-14 1965-05-18 Kelsey Hayes Co Fluid pressure motor mechanism
US3452646A (en) * 1966-12-29 1969-07-01 Bendix Corp Valve and spring retainer
US3845692A (en) * 1972-04-07 1974-11-05 Nisshin Kogyo Kk Vacuum suspended type servo-motor

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4590845A (en) * 1979-12-14 1986-05-27 Tokico Ltd. Pneumatic servo booster
US4398449A (en) * 1980-01-21 1983-08-16 Tokico Ltd. Pneumatic servo booster
US4387625A (en) * 1980-02-09 1983-06-14 Toyota Jidosha Kogyo Kabushiki Kaisha Brake booster
US4643076A (en) * 1980-04-21 1987-02-17 Jidosha Kiki Co., Ltd. Controller for valve mechanism of brake booster
US4416188A (en) * 1980-05-26 1983-11-22 Toyota Jidosha Kogyo Kabushiki Kaisha Brake booster
EP0140187A1 (en) * 1983-10-05 1985-05-08 Nissan Motor Co., Ltd. Brake booster
US4633757A (en) * 1983-10-05 1987-01-06 Nissan Motor Company, Limited Brake booster
US4756231A (en) * 1985-08-13 1988-07-12 Nissan Motor Co., Ltd. Pneumatic brake booster
EP0368679A3 (en) * 1988-11-11 1991-06-26 Tokico Ltd. Tandem type brake booster
US5226291A (en) * 1991-12-17 1993-07-13 General Motors Corporation Vacuum booster diaphragm/support plate retention method
US20140062176A1 (en) * 2012-08-28 2014-03-06 Hitachi Automotive Systems, Ltd. Brake Control Apparatus
US20190031168A1 (en) * 2016-01-25 2019-01-31 Advics Co., Ltd. Negative-pressure type booster device

Also Published As

Publication number Publication date
JPS55114653A (en) 1980-09-04
JPS6149140B2 (enrdf_load_stackoverflow) 1986-10-28

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